from typing import AsyncGenerator
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
import os

DATABASE_URL = os.getenv("DATABASE_URL")

if not DATABASE_URL:
    DB_HOST = os.getenv("DB_HOST", "localhost")
    DB_PORT = os.getenv("DB_PORT", "5432")
    DB_NAME = os.getenv("DB_NAME", "postgres")
    DB_USER = os.getenv("DB_USER", "postgres")
    DB_PASSWORD = os.getenv("DB_PASSWORD", "postgres")
    DATABASE_URL = f"postgresql+asyncpg://{DB_USER}:{DB_PASSWORD}@{DB_HOST}:{DB_PORT}/{DB_NAME}"

engine = create_async_engine(DATABASE_URL, pool_pre_ping=True)

SessionLocal = async_sessionmaker(engine, expire_on_commit=False)

async def get_session() -> AsyncGenerator[AsyncSession, None]:
    async with SessionLocal() as session:
        yield session